Easy opening end unit

ABSTRACT

This disclosure is directed to an easy opening end unit which includes an end panel, an opening in the end panel, the opening being defined by a free end of the end panel, the free edge merging with a line of weakness and collectively bounding a tab joined by the line of weakness to the end panel, an upstanding boss carried by the tab adjacent the line of weakness functioning as means for concentrating an opening force to rupture the line of weakness thereby free the tab for rotational movement relative to the end panel and providing access to a product in a container with which the end unit is associated. The end panel further includes means for limiting radial motion of the boss and an enlargement carried by the boss prevents axial disassembly of the tab relative to the end panel.

United States Patent Peyser et a1.

[ EASY OPENING END UNIT [75] Inventors: Harry A. Peyser, Olympia Fields;

Carmen T. Mascia, Westmont, both of I11.

[73] Assignee: Continental Can Company, Inc.,

New York, NY.

[22] Filed: Feb. 14, 1974 [21] Appl. No.: 442,453

[52] US. Cl 220/268; 220/331 [51] Int. Cl. B65D 39/00 [58] Field of Search 220/27, 54, 48, 33, 260,

[56] References Cited UNITED STATES PATENTS 2,261,117 11/1941 Jack, Jr 220/27 3,731,836 5/1973 Silver 3,813,000 5/1974 Underwood 220/54 Primary ExaminerGeorge T. Hall Attorney, Agent, or FirmDiller, Brown, Ramik & Wight This disclosure is directed to an easy opening end unit which includes an end panel, an opening in the end panel, the opening being defined by a free end of the end panel, the free edge merging with a line of weakness and collectively bounding a tab joined by the line of weakness to the end panel, an upstanding boss carried by the tab adjacent the line of weakness functioning as means for concentrating an opening force to rupture the line of weakness thereby free the tab for rotational movement relative to the end panel and providing access to a product in a container with which the end unit is associated.

ABSTRACT The end panel further includes means for limiting radial motion of the boss and an enlargement carried by the boss prevents axial disassembly of the tab relative to the end panel.

25 Claims, 19 Drawing Figures U3. Patent Oct. 28, 1975 Sheet 10f2 U.S. Patent Oct. 28, 1975 Sheet 2 of2 3,915,333

PQ SH ROWE 40 new 47 EASY OPENING END UNIT The instant invention relates to new and useful improvements in containers, and more particularly to a novel container having an easy-opening end unit or closure.

It is conventional to form easy-opening containers having a tear strip which is not completely torn from the end panel, but remains attached thereto. Such tear strips and the normal pull tab attached thereto cannot therefore be discarded as a unit. This reduces litter to some extent but increases the probability of persons being cut by the sharp raw edge of the tear strip which remains attached to the container and is exposed exteriorly thereof as well as, of course, exteriorly of the associated end unit.

In keeping with the foregoing, it is a primary object of this invention to provide a novel easy-opening end unit which includes an end panel and a tab joined thereto by a line weakness with the tab normally closing an opening in the end panel, and means for mounting the tab for rotation relative to the end panel for exposing the opening therein yet precluding the total disassembly of the tab and end unit whereby the former cannot be intentionally discarded.

A further object of this invention is to provide a novel easy opening end unit of the type defined wherein means in the form of an upstanding boss formed integral from the material of the tab is provided for concentrating an opening force adjacent the line of weakness for rupturing the latter to initiate severance of the tab relative to the end panel and the subsequent rotation of the tab to provide access to the end panel opening.

Yet another object of this invention is to provide a novel easy opening end unit of the type described wherein the means mounting the tab for rotation is defined in part by a portion of the opening which surrounds the hollow upstanding boss or rivet and confines the same against radial disassembly relative to the opening.

A further object of this invention is to provide a novel easy-opening end unit wherein the tab heretofore described is mounted by the tab mounting means for rotation internally of the end panel whereby in the open po sition thereof edges of the tab are unexposed.

A further object of this invention is to provide an easy-opening end unit having an end panel with the opening therein defined by a free edge of the end panel merging with a line of weakness and collectively generally bounding a tab joined by a line of weakness to the end panel, an upstanding boss carried by the tab adjacent the line of weakness functioning as means for concentrating an opening force through the tab to the line of weakness for rupturing the latter, thereby freeing the tab for movement relative to the end panel, the end panel further including means for limiting radial motion of the boss while permitting rotation of motion of the boss relative to the end panel to thereby permit rotational motion of the tab, and an enlargement carried by the boss for preventing axial disassembly of the tab relative to the end panel opening.

Still another object of this invention is to provide an easy-opening unit of the type latter-defined wherein the radial motion limiting means is a space of the opening of a lesser dimension than the diameter of the boss.

Further in accordance with this invention, it is also considered an object thereof to provide a novel method of manufacturing an easy-opening end unit of the type heretofore described by forming a tab from an end panel of an end unit which has a predetermined peripheral boundary along which the tab is removable from the end panel to define an opening therein, severing the peripheral boundary by a line of severance along a major extent thereof, weakening the peripheral boundary by a line of weakness along a minor extent thereof, forming a stem from the material of the tab adjacent an inboard of the line of weakness, forming a restricted area in the end panel of a dimension less than that of the stem along the peripheral boundary, and forming an enlarged head upon the stem of a dimension sufficient to be disposed outboard of the line of weakness whereby upon the rupture of the line of weakness by an axial opening force applied to the enlarged head, the tab is precluded by the enlarged head from axial disassembly relative to the opening and is as well precluded from radial disassembly by the dimensioned restricted area.

Still another object of this invention is to provide a novel method including the further step of underlying a periphery of the tab relative to the line of severance outboard thereof.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawings:

In the drawings:

FIG. 1 is a perspective view of the novel easy-opening end unit constructed in accordance with this invention, and illustrates an end panel having an opening closed by a tab secured to the end panel by a line of weakness such that upon rupture of the line of weakness the tab is free to rotate to form a pour opening in the end unit.

FIG. 2A and B are respective fragmentary enlarged top plan and radial sectional views taken through the end unit of FIG. 1, and illustrate the first operation of a method of forming the end unit by raising a portion of the end panel along a boundary line contoured generally to the configuration of the tab.

FIG. 3A and B are views identical to FIG. 2A and B, respectively, and further illustrate the second operation of the method wherein a bubble formed by the first operation is re-formed into a rivet area.

FIG. 4A and B and C are views similar to FIGS. 2 and 3 and illustrate the third operation of the method wherein a major severance line along the boundary of the tab in a minor score line or line of weakness define the outboard area of the tab.

FIG. 5A and B are views similar to FIGS. 2 through 4, and illustrate the manner in which a major portion of the tab is flattened to undercover a major free peripheral edge of the end panel defining the opening therein.

FIG. 6A and B are views similar to FIGS. 2 through 5 and illustrate the fifth operation of the method in which an enlargement or rivet head is formed having a radial dimension in excess of that of the line of weakness.

FIG. 7 is a fragmentary view of the underside of the end unit after the performance of the fifth operation, and illustrates the sixth operation of the method wherein sealing compound is applied about a major portion of the outline of the tab periphery.

FIG. 8 is an enlarged fragmentary top plan view of the easy opening end unit of FIG. 1. and illustrates in detail the outline of the tab, the opening of the end panel defined by a major line of severance and a minor line of weakness, and the manner in which a rivet is integrally formed from the material of the tab in the area of the line of weakness.

FIG. 9 is a sectional view taken generally along the line 9-9 of FIG. 8, and illustrates the details of the end unit as well as the manner in which the latter is double seamed to a can body.

FIG. 10 is a fragmentary sectional view similar to FIG. 9, and illustrates the manner in which after an absolutely directed force severs the line of weakness the tab is rotated beneath the end unit to permit a produce within the can to be dispensed through the end panel opening.

FIG. 11 is a fragmentary sectional view taken generally along the line 11-11 of FIG. 8, and illustrates the details in the rivet area of the tab.

FIG. 12 is an enlarged fragmentary sectional view taken generally along the line 1212 of FIG. 9, and illustrates the details of the severance line, the line of weakness, and sealing compound in the area of the line of severance.

FIG. 13 is a fragmentary perspective view of the container and end unit, and illustrates the tab rotated to a position partially opening the end panel opening.

In a novel easy-opening end unit constructed in accordance with this invention is illustrated in FIGS. 1 and 8 through 13 of the drawings, and is generally designated by the reference numeral 10. The easy-opening end unit 10 is preferably constructed from metallic material and includes an end panel 11 of a generally circular configuration terminating at its periphery (unnumbered) at an upwardly opening bead 12 (FIG. 9), a chuck wall 13, and a flange 14 which with an upper pe riphery or flange (unnumbered) ofa container body 15 defines a conventional double seam 16.

A tab 17 is joined to the end panel 11 by an arcuate score line or line of weakness 18 which subtends an angle of approximately 90 degrees. The tab 17 is further defined by a lanced or severed terminal. free edge which is generally designated by the reference numeral 20 and includes two arcuate edges 21,22 to either side of the line of severance 18, (FIG. 8) which converge toward each other in a direction from left-to-right as viewed in FIG. 8 and define abrupt radius edge portions 23,24 beyond which the last edge or line of severance 20 includes the respective diverging edge portions 25,26 again as viewed from left-to-right in FIG. 8. Beyond the diverging edge portions 25,26, the severance line 20 includes respective radius edge portions 27,28 followed by gradually converging edge portions 30.31 which blend with the radius portions 32,33 in turn joined by an edge portion 34 remote from the line of severance 18. Thus, the overall configuration of the peripheral boundary of the tab 17 as viewed from leftto-right in FIG. 8 includes the arcuate line of weakness 18, and thereafter the totality of the line of severance 20 which includes the severance or severed edge portions 21 through 28 and 30 through 34. Inboard of the score line 18 and the severed edge 20 the latter two collectively define a border or peripheral edge 35 of the tab 18.

The end panel 17 is provided adjacent the edge portion 34 with an upstanding arcuate boss 36 whereas radially remote therefrom the tab 17 is provided with means, generally designed by the reference numeral 40 (FIGS. 8 and 9) for concentrating an opening force to the line of weakness 18 through the tab 17 for rupturing the line of weakness 18 in a manner to be described more fully hereinafter with respect to FIG. 10. The force concentrating means 40 includes an upstanding hollow boss having a generally cylindrical stem 41 and a flattened enlarged head 42 which defines a conventional rivet, although the function thereof is not that of joining one element to another but rather to (1) provide the force concentration heretofore noted and (2) prevent total disassembly of the tab 17 from the end panel 11 upon the rupture of the line of weakness 18, as will be described more fully hereinafter. The enlarged head 42 is ofa radial dimension greater than that of the line of weakness 18 and the severed edges 21, 22 as well as the sharp radius edges 23,24, as is most readily apparent from FIGS. 8 and 9 of the drawings. The function of the latter will be described more fully hereinafter.

The end panel 11 of the end unit 10 includes an opening which is generally designated by the reference numeral 47 and inasmuch as the latter is formed by the same score line 18 and line of severance 20 as that which forms the tab 17 the opening 47 has applied to its edge reference numerals corresponding to those associated with the tab 17 but additionally being primed. As an example, the opening 47 of the end panel 11 includes the arcuate score line 18 upon the rupture of the latter. Moreover, pursuant to the method of forming the end unit 10 in a manner to be described more fully hereinafter, the end panel opening 47 includes severed edge portions 21, 22' which are adjacent the severed edge portions 21,22. Likewise, the reference numerals 23' through 28 and 30 through 34' indicate edge portions of the opening 47 which are adjacent to the edge portions 23 through 28 and 30 through 34 of the tab 17.

As is best illustrated in FIGS. 8 and 9, the peripheral edge 35 of the tab 17 underlies the end panel 11 radially outboard of the severed edge 47 about substantially the entirety of the edges 20,47, and this area is internally coated with suitable sealing compound (FIGS. 9 and 11).

Assuming it is desired to obtain access to the contents (not shown) of the container 15 (FIG. 9) a downwardly directed axial force is applied to the means 40 and may also be applied to the boss 36 in the manner indicated by the unnumbered headed arrows in FIG. 9 bearing the caption PUSH. Such a downwardly directed axial force (or forces) results in the fracture of the score line or line of weakness 18 and the sealing compound S in the manner illustrated in FIG. 10. Thus the tab 17 is totally free from the end panel 11 and it may be rotated clockwise or counterclockwise (FIG. 13) by one merely grasping the enlarged head 42 of the rivet 40 and applying suitable rotational force thereto, in the manner shown best in FIG. 13 in which the tab 17 has been partially rotated counterclockwise to partially open the opening 47 of the end panel 11. It is of importance in keeping with this invention that the enlarged head 42 is radially larger than the radius of the line of weakness 18 and the radius of the edge portions 2l,22 of the opening 47 so that the tab 17 cannot drop into the interior of the container 15 but instead will be held suspended by the outboard portions of the end panel 11 adjacent the edge portions 21 ',22, in the manner best illustrated in FIG. 10. Likewise, the diameter of the stem 41 must be greater than the distance between the edges 23',24 of the opening 47 so that disassembly of the tab 17 cannot take place by a left-toright shifting of the tab 17 relative to the panel 11 as viewed in FIG. 8. Thus, by the structure described once the tab 17 has been removed from the end panel 11 by the rupture of the score line 18, the tab 17 cannot (1) be totally disassembled from theend panel by relative radial motion therebetween and (2) cannot be totally disassembled from the end panel 11 by relative axial motion therebetween. Once having been opened, the tab 17 may be re-rotated to its original position to close the opening 47, although perfect hermetic sealing cannot be obtained by the latter action.

Reference is now made specifically to FIGS. 2 through 7 of the drawings to which like reference numerals have been applied in order to described the method of manufacturing the easy opening end unit of FIGS. 1 and 8 through 13.

Apart from the conventional formation of the easy opening end unit 10 the method of forming the specific structure of the structure inboard of the bead 12 is best illustrated in successive FIGS. 2 through 7 of the drawings to which attention is now directed.

The first operation in forming the easy opening end unit 10 is that of raising a portion 50 (FIGS. 2A and B) of the end panel 11 to form the arcuate embossment 36 and a bubble 51 which is eventually re-formed into the means 40. A boundary wall 52 rising from the end panel 11 is contoured generally to the over-all configuration of the tab 17 and the opening 47, as is most readily apparent from a comparison of FIG. 2A and 8 of the drawings.

Following the first operation the bubble 51 of FIGS. 2A and B is re-formed to a generally cylindrical bubble 53 of FIGS. 3A and B.

Following the second operation illustrated in FIGS. 3A and B a third operation is performed by conventionally forming the score line 18 in the end panel 11, (FIG. 4A and B) and lancing or severing the end panel 11, as indicated by the reference numberal 54 in FIG. 4A and B. The lancing or severing operation in effect forms the severed edge portions 21 through 28 and 30 through 34 defining the free edge of the tab 17 and the severed edges 21' through 28' and 30' through 34' which define the opening 47 of the end panel 11.

Following the scoring and lancing operation of FIG. 4 the boundary wall 52 (FIG. 2A and B) is flattened such that the periphery 20 of the tab 17 underlies the opening 47 of the end panel 11 along the portions 21' through 28 and 30 through 34 of the end panel opening 47.

Thereafter the generally cylindrical boss 53 (FIG. 3) is re-formed in a fifth operation (FIG. 6A and B) to form the stem 41 and the enlarged head 42, after which (FIG. 7) the sealing compound S is applied to the underside of the end unit 10 in the over-all area of the opening 47, excluding the line of weakness 18, although the sealing compound S could likewise be applied thereover.

From the foregoing, it is to be particularly noted that the tab 17 and the means 40 are formed from the material of the end panel 11, and due to the dimensional relationship earlier noted, total disassembly of the tab 17 relative to end panel 11 is precluded either by (1) direct axial or relative motion therebetween or (2) direct radial motion therebetween. Thus, in keeping with the method the relatively inexpensive and unitary structure 10 is readily manufactured and in operation disadvantageous disassembly of the tab 17 relative to the end panel 11 is totally precluded.

While preferred forms and arrangement of parts have been shown in illustrating the invention, it is to be clearly understood that various changes in details and arrangement of parts may be made without departing from the scope and spirit of this disclosure.

We claim:

1. An easy opening end unit comprising an end panel, a tab joined by a line of weakness to said end panel, said tab normally closing an opening in said end panel, means for concentrating an opening force through said tab adjacent said line of weakness for rupturing the latter, and means mounting said tab for rotation relative to said end panel about an axis through said opening for exposing said opening.

2. The easy opening end unit as defined in claim 1 wherein said force concentrating means is an upstanding boss carried by said tab adjacent said line of weak ness.

3. The easy opening end unit as defined in claim 1 wherein said force concentrating means is a hollow upstanding boss integrally formed from the material of said tab adjacent said line of weakness.

4. The easy opening end unit as defined in claim 1 wherein said rotation mounting means is defined at least in part by a portion of said opening at least in part surrounding said force concentrating means.

5. The easy opening end unit as defined in claim 1 wherein said rotation mounting means is defined at least in part by a portion of said opening at least in part surrounding said force concentrating means, and means for precluding complete disassembly of said tab relative to said end panel upon the rupturing of said line of weakness.

6. The easy opening end unit as defined in claim 1 wherein said tab is mounted by said tab mounting means for rotation internally of said end panel.

7. The easy opening end unit as defined in claim 1 wherein said end panel'opening is defined by said line of weakness and a free edge of said end panel, and said line of weakness and free edge define the peripheral boundary of said end panel opening.

8. The easy opening end unit as defined in claim 1 wherein said end panel opening is defined by said line of weakness and a free edge of said end panel, said line of weakness and free edge define the peripheral boundary of said end panel opening, and said tab includes a peripheral edge portion projecting radially outwardly beyond said free edge thereby covering that portion of the end panel opening defined thereby.

9. The easy opening end unit as defined in claim 1 wherein said end panel opening is defined by said line of weakness and a free edge of said end panel, said line of weakness and free edge define the peripheral boundary of said end panel opening, said tab includes a pcripheral edge portion projecting radially outwardly beyond said free edge thereby covering that portion of the end panel opening defined thereby, and means for forming a seal between the peripheral edge portion of said tab and said end panel in the area defined by said end panel free edge.

10. The easy opening end unit as defined in claim 1 wherein said tab rotation mounting means is in part defined by said force concentrating means, said lastmentioned part is an upstanding boss carried by said tab adjacent said line of weakness, said tab rotation mounting means is further defined by a peripheral area of said end panel radially outboard of said line of weakness and a peripheral area of said end panel radially outboard of a free edge of said end panel forming a continuation of said line of weakness, and said peripheral areas surround said upstanding boss for more than 180 and less than 360.

11. The easy opening end unit as defined in claim 1 wherein said tab rotation mounting means is in part defined by said force concentrating means, said lastmentioned part is an upstanding boss carried by said tab adjacent said line of weakness, said tab rotation mounting means is further defined by a peripheral area of said end panel radially outboard of said line of weakness and a peripheral area of said end panel radially outboard of a free edge of said end panel forming a continuation of said line of weakness, said peripheral areas surround said upstanding boss for more than 180 and less than 360, and said upstanding boss has an enlarged head projecting radially over at least a portion of one of said peripheral areas whereby upon the rupture of said line of weakness said tab is precluded from total disassembly relative to said end panel.

12. The easy opening end unit as defined in claim 1 wherein said tab rotation mounting means is in part defined by said force concentrating means, said lastmentioned part is an upstanding boss carried by said tab adjacent said line of weakness, said tab rotation mounting means is further defined by a peripheral area of said end panel radially outboard of said line of weakness and a peripheral area of said end panel radially outboard of a free edge of said end panel forming a continuation of said line of weakness, said peripheral areas surround said upstanding boss for more than 180 and less than 360, said upstanding boss has an enlarged head projecting radially over at least a portion of one of said peripheral areas whereby upon the rupture of said line of weakness said tab is precluded from total disassembly relative to said end panel, and said tab is mounted for rotation by said tab mounting means for rotation internally of said end panel.

13. The easy opening end unit as defined in claim 1 wherein said tab rotation mounting means is in part defined by said force concentrating means, said lastmen'tioned part is an upstanding boss carried by said tab adjacent said line of weakness, said tab rotation mounting means is further defined by a peripheral area of said end panel radially outboard of said line of weakness and a peripheral area of said end panel radially outboard of a free edge of said end panel forming a continuation of said line of weakness, said peripheral areas surround said upstanding boss for more than 180 and less than 360, said upstanding boss has an enlarged head projecting radially over at least a portion of one of said peripheral areas whereby upon the rupture of said line of weakness said tab is precluded from total disassembly relative to said end panel, said tab is mounted for rotation by said tab mounting means for rotation internally of said end panel, and said tab includes a peripheral edge portion projecting radially outwardly beyond said free edge thereby underlyingly covering that portion of the end panel opening defined thereby.

14. An easy opening end unit comprising an end panel, an opening in said end panel, said opening being defined by a free edge of said end panel, said free edge merging with a line of weakness and collectively generally bounding a tab joined by said line of weakness to said end panel, an upstanding boss carried by said tab adjacent said line of weakness functioning as means for concentrating an opening force through said tab to said line of weakness for rupturing the latter thereby freeing the tab for movement relative to the end panel, said end panel including means for limiting radial motion of said boss while permitting rotational motion of said boss relative to said end panel, and an enlargement carried by said boss for preventing axial disassembly of said tab relative to said end panel.

15. The easy opening end unit as defined in claim 14 wherein said radial motion limiting means is a space of said opening of a lesser dimension than said boss.

16. An easy opening end unit comprising an end panel, a tab joined by a line of weakness to said end panel, said tab normally closing an opening in said end panel, and means mounting said tab for rotation relative to said end panel about an axis through said opening whereby upon the rupture of said line of weakness said tab may be rotated about said axis for exposing said opening.

17. The easy opening end unit as defined in claim 16 wherein said rotation mounting means includes a neck of a headed rivet carried by said tab, a portion of a periphery of said opening at least partially surrounds said neck, and said opening portion has a minimum dimension as measured tangentially of said neck which is less than the diameter of said neck whereby said rivet is confined against movement past said minimum dimension.

18. The easy opening end unit as defined in claim 1 wherein the diameter of said rivet head is greater than a dimension of said opening portion measured through said axis whereby said rivet head overlies radially beyond said opening portion and precludes the axial disassembly of said tab and opening.

19. The easy opening end unit as defined in claim 18 wherein said rivet head is disposed at an exterior surface of said end panel.

20. The easy opening end unit as defined in claim 19 wherein said line of weakness is at least in part defined by a score line.

21. The easy opening end unit as defined in claim 19 wherein said line of weakness is defined by a score line and a cut line through said end panel.

22. The easy opening end unit as defined in claim 21 wherein said score line and cut line define an arc of greater than partially surrounding said rivet neck.

23. An easy opening end unit comprising an end panel, a tab in said end panel formed from the material thereof, said tab being setoff by a continuous peripheral boundry line, said continuous peripheral boundry line corresponding in outline to an opening formed in said end panel upon the displacement of said tab relative to said end panel, a rivet carried by said tab, said rivet having a neck and an enlarged head, said head being disposed on an exterior side of said end panel, a portion of said continuous peripheral boundry line surrounds said neck through an are greater than 180 and less than 360, said last-mentioned portion has a miniopening.

24. The easy opening end unit as defined in claim 23 wherein said boundry line is defined by a score line at least partially surrounding said rivet.

25. The easy opening end unit as defined in claim 24 wherein the remainder of said boundry line is defined by a through cut line. 

1. An easy opening end unit comprising an end panel, a tab joined by a line of weakness to said end panel, said tab normally closing an opening in said end panel, means for concentrating an opening force through said tab adjacent said line of weakness for rupturing the latter, and means mounting said tab for rotation relative to said end panel about an axis through said opening for exposing said opening.
 2. The easy opening end unit as defined in claim 1 wherein said force concentrating means is an upstanding boss carried by said tab adjacent said line of weakness.
 3. The easy opening end unit as defined in claim 1 wherein said force concentrating means is a hollow upstanding boss integrally formed from the material of said tab adjacent said line of weakness.
 4. The easy opening end unit as defined in claim 1 wherein said rotation mounting means is defined at least in part by a portion of said opeNing at least in part surrounding said force concentrating means.
 5. The easy opening end unit as defined in claim 1 wherein said rotation mounting means is defined at least in part by a portion of said opening at least in part surrounding said force concentrating means, and means for precluding complete disassembly of said tab relative to said end panel upon the rupturing of said line of weakness.
 6. The easy opening end unit as defined in claim 1 wherein said tab is mounted by said tab mounting means for rotation internally of said end panel.
 7. The easy opening end unit as defined in claim 1 wherein said end panel opening is defined by said line of weakness and a free edge of said end panel, and said line of weakness and free edge define the peripheral boundary of said end panel opening.
 8. The easy opening end unit as defined in claim 1 wherein said end panel opening is defined by said line of weakness and a free edge of said end panel, said line of weakness and free edge define the peripheral boundary of said end panel opening, and said tab includes a peripheral edge portion projecting radially outwardly beyond said free edge thereby covering that portion of the end panel opening defined thereby.
 9. The easy opening end unit as defined in claim 1 wherein said end panel opening is defined by said line of weakness and a free edge of said end panel, said line of weakness and free edge define the peripheral boundary of said end panel opening, said tab includes a peripheral edge portion projecting radially outwardly beyond said free edge thereby covering that portion of the end panel opening defined thereby, and means for forming a seal between the peripheral edge portion of said tab and said end panel in the area defined by said end panel free edge.
 10. The easy opening end unit as defined in claim 1 wherein said tab rotation mounting means is in part defined by said force concentrating means, said last-mentioned part is an upstanding boss carried by said tab adjacent said line of weakness, said tab rotation mounting means is further defined by a peripheral area of said end panel radially outboard of said line of weakness and a peripheral area of said end panel radially outboard of a free edge of said end panel forming a continuation of said line of weakness, and said peripheral areas surround said upstanding boss for more than 180* and less than 360*.
 11. The easy opening end unit as defined in claim 1 wherein said tab rotation mounting means is in part defined by said force concentrating means, said last-mentioned part is an upstanding boss carried by said tab adjacent said line of weakness, said tab rotation mounting means is further defined by a peripheral area of said end panel radially outboard of said line of weakness and a peripheral area of said end panel radially outboard of a free edge of said end panel forming a continuation of said line of weakness, said peripheral areas surround said upstanding boss for more than 180* and less than 360*, and said upstanding boss has an enlarged head projecting radially over at least a portion of one of said peripheral areas whereby upon the rupture of said line of weakness said tab is precluded from total disassembly relative to said end panel.
 12. The easy opening end unit as defined in claim 1 wherein said tab rotation mounting means is in part defined by said force concentrating means, said last-mentioned part is an upstanding boss carried by said tab adjacent said line of weakness, said tab rotation mounting means is further defined by a peripheral area of said end panel radially outboard of said line of weakness and a peripheral area of said end panel radially outboard of a free edge of said end panel forming a continuation of said line of weakness, said peripheral areas surround said upstanding boss for more than 180* and less than 360*, said upstanding boss has an enlarged head projecting radially over at least a portion of one of said periPheral areas whereby upon the rupture of said line of weakness said tab is precluded from total disassembly relative to said end panel, and said tab is mounted for rotation by said tab mounting means for rotation internally of said end panel.
 13. The easy opening end unit as defined in claim 1 wherein said tab rotation mounting means is in part defined by said force concentrating means, said last-mentioned part is an upstanding boss carried by said tab adjacent said line of weakness, said tab rotation mounting means is further defined by a peripheral area of said end panel radially outboard of said line of weakness and a peripheral area of said end panel radially outboard of a free edge of said end panel forming a continuation of said line of weakness, said peripheral areas surround said upstanding boss for more than 180* and less than 360*, said upstanding boss has an enlarged head projecting radially over at least a portion of one of said peripheral areas whereby upon the rupture of said line of weakness said tab is precluded from total disassembly relative to said end panel, said tab is mounted for rotation by said tab mounting means for rotation internally of said end panel, and said tab includes a peripheral edge portion projecting radially outwardly beyond said free edge thereby underlyingly covering that portion of the end panel opening defined thereby.
 14. An easy opening end unit comprising an end panel, an opening in said end panel, said opening being defined by a free edge of said end panel, said free edge merging with a line of weakness and collectively generally bounding a tab joined by said line of weakness to said end panel, an upstanding boss carried by said tab adjacent said line of weakness functioning as means for concentrating an opening force through said tab to said line of weakness for rupturing the latter thereby freeing the tab for movement relative to the end panel, said end panel including means for limiting radial motion of said boss while permitting rotational motion of said boss relative to said end panel, and an enlargement carried by said boss for preventing axial disassembly of said tab relative to said end panel.
 15. The easy opening end unit as defined in claim 14 wherein said radial motion limiting means is a space of said opening of a lesser dimension than said boss.
 16. An easy opening end unit comprising an end panel, a tab joined by a line of weakness to said end panel, said tab normally closing an opening in said end panel, and means mounting said tab for rotation relative to said end panel about an axis through said opening whereby upon the rupture of said line of weakness said tab may be rotated about said axis for exposing said opening.
 17. The easy opening end unit as defined in claim 16 wherein said rotation mounting means includes a neck of a headed rivet carried by said tab, a portion of a periphery of said opening at least partially surrounds said neck, and said opening portion has a minimum dimension as measured tangentially of said neck which is less than the diameter of said neck whereby said rivet is confined against movement past said minimum dimension.
 18. The easy opening end unit as defined in claim 1 wherein the diameter of said rivet head is greater than a dimension of said opening portion measured through said axis whereby said rivet head overlies radially beyond said opening portion and precludes the axial disassembly of said tab and opening.
 19. The easy opening end unit as defined in claim 18 wherein said rivet head is disposed at an exterior surface of said end panel.
 20. The easy opening end unit as defined in claim 19 wherein said line of weakness is at least in part defined by a score line.
 21. The easy opening end unit as defined in claim 19 wherein said line of weakness is defined by a score line and a cut line through said end panel.
 22. The easy opening end unit as defined in claim 21 wherein said score line and cut line define an arc of greater thaN 180* partially surrounding said rivet neck.
 23. An easy opening end unit comprising an end panel, a tab in said end panel formed from the material thereof, said tab being set-off by a continuous peripheral boundry line, said continuous peripheral boundry line corresponding in outline to an opening formed in said end panel upon the displacement of said tab relative to said end panel, a rivet carried by said tab, said rivet having a neck and an enlarged head, said head being disposed on an exterior side of said end panel, a portion of said continuous peripheral boundry line surrounds said neck through an arc greater than 180* and less than 360*, said last-mentioned portion has a minimum dimension as measured tangentially of said neck which is less than the diameter of said neck whereby said rivet is confined against movement past said minimum dimension, and the diameter of said rivet head is greater than a dimension of said last-mentioned portion measured through an axis of said rivet whereby said rivet head overlies radially beyond said last-mentioned portion and precludes axial disassembly of said tab and opening.
 24. The easy opening end unit as defined in claim 23 wherein said boundry line is defined by a score line at least partially surrounding said rivet.
 25. The easy opening end unit as defined in claim 24 wherein the remainder of said boundry line is defined by a through cut line. 